The disclosed embodiments relate to circuit breaker current paths for providing additional current capability.
Circuit breakers are generally implemented to protect equipment from overcurrent situations, for example, when a short circuit or ground fault occurs in an electrical supply conductor. Upon the occurrence of an overcurrent condition, electrical contacts within the circuit breaker will generally open, stopping the supply of electrical current to the equipment. Designs for circuit breakers generally include accommodations for both high quiescent currents and high withstand currents. To maintain a high withstand current rating, the contacts must be locked closed at the current withstand rating and be able to withstand the large electrodynamic repulsion forces generated by the current flow.
Multipole circuit breakers include a variety of construction implementations such as blow open and non-blow open contact arms, overcentering and non-overcentering contact arms, single contact pair arrangements with the contact pair at one end of a contact arm and a pivot at the other end thereof, double contact pair arrangements, sometimes referred to as rotary breakers, with a contact pair at each end of a contact arm and a contact arm pivot intermediate or centrally located between the two ends, and single housing constructions with the circuit breaker components housed within a single case and cover. Other implementations include cassette type constructions with the current carrying components of each phase housed within a phase cassette and each phase cassette housed within a case and cover that also houses an operating mechanism.
Multipole circuit breakers are generally available in two, three, and four pole arrangements, with the two and three pole arrangements generally used in two and three phase circuits, respectively. Four pole arrangements are typically employed on three phase circuits having switching neutrals, where the fourth pole operates to open and close the neutral circuit in a coordinated arrangement with the opening and closing of the primary circuit phases.
Generally, each pole in a multiphase circuit breaker system is provided with a current sensing element that generates a trip signal which is used to trip the circuit breaker. Each pole may carry a significant amount of current. FIG. 1 shows a diagram of an exemplary circuit breaker 100 for a single phase. Breaker 100 includes a fixed contact assembly 105 and a movable contact assembly 110 that pivots about a rotation point 140. The movable contact assembly 110 may include one or more first arcing contacts 120 and one or more first main contacts 125 mounted on one or more finger assemblies 145.
The one or more finger assemblies 145 may operate to provide a mounting point for the one or more first arcing contacts 120 and one or more first main contacts and to provide a conduction path between the arcing and main contacts and a movable assembly load terminal 150. The one or more finger assemblies 145 may be resilient to allow the finger assemblies to pivot about a pivot point 115. The one or more finger assemblies 145 may also provide a spring force to assist in opening the circuit breaker contacts with a desired velocity upon an overcurrent occurrence.
The fixed contact assembly 105 may include one or more second arcing contacts 130 and one or more second main contacts 135. The fixed contact assembly 105 may also include a fixed assembly load terminal 155 on which the one or more second arcing contacts 130 and one or more second main contacts 135 may be mounted. The fixed and movable contact assemblies 105, 110 are generally constructed to withstand closing on a fault and thus have a significant current carrying capability.
It would be advantageous to provide a circuit breaker system with an increased current carrying capability.